(1) Field of the Invention
The present invention relates to a disk apparatus in which a head carriage with a read/write head supported thereon is shifted in a radial direction of a disk by a head actuator and the head reads information from or writes information to the disk.
(2) Description of the Related Art
Many personal computers and wordprocessors employ a magnetic disk drive as a storage device. In the magnetic disk drive, a disk cartridge, accommodating a magnetic disk, is inserted and placed at a disk-loaded position within the magnetic disk drive, a read/write head is shifted in a radial direction of the disk, and the read/write head accesses the disk when the disk is rotated.
The magnetic disk drive of the above type includes a disk holder and a slider which constitute a disk transporting mechanism. The disk holder holds the disk cartridge, and the disk cartridge is inserted into or ejected from the disk holder. The slider is moved by the insertion of the disk cartridge, and the disk holder is moved from an insert/eject position to a disk-loaded position by the movement of the slider.
The magnetic disk drive of the above type includes a head carriage having a head arm on which an upper head is supported and a carriage body on which a lower head is supported. When the disk cartridge inserted in the disk holder is placed at the disk-loaded position, the lower head of the head carriage is brought into contact with the bottom surface of the disk, and the head arm of the head carriage is lowered so as to bring the upper head into contact with the top surface of the disk. By using the upper and lower heads in this condition, the magnetic disk drive accesses the disk when the disk is rotated.
Recently, the use of a large-capacity magnetic disk has grown, and there is an increasing demand for a magnetic disk drive capable of speedily accessing the large-capacity magnetic disk at a high recording density. For use in such a disk drive, a read/write head which is levitated from the disk by an air flow between the disk and the head when the disk is rotated at a high speed is known.
In the magnetic disk drive of the above, the head carriage with the read/write head supported thereon is shifted in a radial direction of the disk by an actuating force of a voice coil motor so as to perform a seek of the read/write head for a desired location of the disk.
Further, there are known two kinds of head carriage mechanism which are used by existing magnetic disk drives to achieve the above-described function: (1) a head carriage mechanism in which a pair of voice coil motors are provided on both sides of the head carriage; and (2) a head carriage mechanism in which a single voice coil motor is provided in the center of the lower part of the head carriage.
In the head carriage mechanism of the kind (1) above, it is necessary that two voice coil motors are provided on the sides of the head carriage, and the cost becomes high and the weight becomes large. The head carriage mechanism of this kind has some disadvantages. For example, during an impact test, a large force is exerted by the head carriage due to the large weight. Misalignment of the elements of the head carriage mechanism is likely to take place if a small error of the position of the disk drive is produced.
In the head carriage mechanism of the kind (2) above, the head carriage is shifted by using a single voice coil motor. The voice coil motor must be mounted in the head carriage mechanism of this kind such that the coil is located in the center of the lower part of the head carriage and the yoke passes through the center of the head carriage. Hence, the elements of the head carriage must be placed so as to match the mounted position of the voice coil motor. As a result, the total height of the head carriage mechanism becomes high. It is difficult to provide a small-size head carriage when the head carriage mechanism of this kind is used.